1. The Field of Invention
The present invention relates to implantable vascular devices for the purpose of access to the body's circulation. More particularly, this invention provides a novel means for intermittent vascular access without the use of indwelling catheters or constant flow shunt structures thus reducing the thrombotic and hemodynamic consequences of other available devices.
2. Related Art
The advent of hemodialysis for the treatment of End-stage Renal Disease has prompted the development of many vascular access devices for the purpose of acquiring large quantities of blood for passage through an extra-corporeal circuit during the hemodialysis procedure. Available devices have consisted of devices employing indwelling venous catheters or flow through shunt devices which create an artificial fistula between an artery and vein.
Current catheter technologies are limited by relatively poor flows and by their tendency to be irritative resulting in vessel stenosis, thrombosis, and occasionally vessel perforation. They frequently dysfunction for mechanical reasons related to the vessel wall, catheter positioning, or thrombus formation in the catheter lumen. For catheter devices that are partially external, infections are frequent due to the chronic breach in the skin, often with severe or even fatal consequences.
Flow through shunt devices which cream a fistulous connection between artery and vein have been the mainstay of modem vascular access for dialysis. These devices are likewise fraught with hazards. Installation of these "shunts" is an extensive surgical procedure resulting in significant tissue trauma and pain. Once in place, the shunts result in additional cardiac output needs with as much as one-fifth of the cardiac output (approximately 1000 ml per minute) required for adequate function. In addition, the transfer of the arterial pressure wave results in damage to the vein at the anastomosis with the shunt resulting in intimal hyperplasia and subsequent shunt occlusion or thrombosis. When this occurs, another vein segment must be used for shunt revision, and exhaustion of available sites is distressingly common. The expense both in terms of health care dollars and human misery is enormous. Repeated punctures of the wall of the shunt result in eventual failure and surgery to repair or replace the shunt.
Each of the available access technologies mentioned thus far are also complicated by the possibility of recirculation of blood already passed through the extra-corporeal circuit resulting in loss of treatment efficiency. The harm done to patients by the "recirculation syndrome" is insidious and at times undetected until great harm has been done.